.a_background {
    width: 100%;
    height: 100%;
    position: absolute;
}

.a_background_top{
    width: 100%;
    height: 71.6%;
    background-image: url("../images/background/a_background_top.png");
    background-size: 100% 100%;
}


.a_background_middle{
    width: 100%;
    height: 13.1%;
    background-image: url("../images/background/a_background_middle.png");
    background-size: 100% 100%;
}

.a_background_botton{
    width: 100%;
    height: 15.3%;
    background-image: url("../images/background/a_background_botton.png");
    background-size: 100% 100%;
}
/*太阳*/
 #sun{
            background: url("../images/sun.png") no-repeat;
            position: absolute;
            z-index: 1;
            top: -30px;
            height: 201px;
            width: 201px;
            right: 5%;
             animation:sun_move linear 50000ms;
             -webkit-animation:sun_move linear 50000ms;
             -moz-animation:sun_move linear 50000ms;
 }
 @keyframes sun_move{
    0%{  transform: translateX(0) translateY(0);}
    100% { transform: translateX(-2000px) translateY(200px);}
 }
 /*云*/

.cloud {   z-index: 2;  position: absolute;  }     
.cloud1 {
            width: 181px;
            height: 101px;
            left: 5%;
            top: 15%;
            background: url("../images/cloud1.png");
}  
.cloud2 {
            width: 301px;
            height: 140px;
            right: 5%;
            background: url("../images/cloud2.png");
}